[philco fan]

i know,its not a philco but i just purchased an entire collection of radios from a retiring radio nut,about 60 in all but as a newby i thought it was a good idea, can't find a schematic on this one,not even on nostalgia air, need to know what the electolytic cap values are,its unmarked,its a three-section,thanks,phil. does anyone know how to bypass the interstage trans on a philco model 77? it uses two 45's and rons website doesn't cover it,thanks again,phil

[Guest]

Is there a letter before that 50 model number? What tubes does it use?

[philco fan]

there's no lable or i.d. on radio,got the model number from radioatticarchives,its a clock/radio,a 4 tuber,35z5,50l6,12sg7,12sq7 and a number stamped on the chassis,44987.thanks for the reply,phil

[rghines1]

Follow the link below to the Schematic Bank. Schematics are in djvu format. There are utilities for viewing this format on the site. The caps are 40uF and 30uF in the power supply. No mention of voltage. 160V caps should work fine. A 20uf used for a cathode bypass. I'd go with a 25V cap for the bypass cap.

http://techpreservation.dyndns.org
Richard

[philco fan]

thanks to carl and to richard,got the info on the caps,able to fire it up after replacing 3 out of the 4 tubes,no audio at all,found what i think is a flexable resistor? connected between pin 2 of 35z5 and a terminal strip,replaced it with a 15 ohm i had handy,original was 22 ohms,still no audio,would this small resistance difference stop it from working?thanks again,phil

[rghines1]

Replacing with 15 ohm resister should still work. However I'd want to put a 22 ohm or slightly higher when you get one with today's higher line voltage.

Check the plate voltage on the audio output tube. Expect to see about 100V.
If not check further for a problem in the power supply or open audio output transformer.

Richard

[philco fan]

thanks to carl and richard i got it fired up today,found bad tube connections at the 12sq7's socket,cleaned and tightened them and she fired up!! i know its a cheap little set but its a great victory for newby! now, how about some help on that philco 77? do you guys know how to bypass the trans? tests open ckt on both side,thanks,phil

[Terry Judkins]

Hammond interstage transformers are available from RadioDaze for around $15.00 plus shipping. I just bought one for a Philco 640 and it works fine. The pushpull output in your 77 requires phase inversion which is provided by the interstage transformer. I know of no practical way to 'bypass' the transformer and still provide phase inversion.

[philco fan]

thanks terry,do you know the part number?

[Terry Judkins]

HX124A should work.

[Ed Locker]

Will this do you any good?

http://www.philcoradio.com/tech/audio.htm

[philco fan]

ed57,will any of these circuits work on this 77? its using two 45's as outputs,tried the circuit on ron's site ,got some results but not good ones, i now have audio but VERY LOW and one of the 45's gets really hot so i shut it down quick. let me know which one should work,both sides of the interstage check open,i don't want to act like i know what i'm doing,i really don't,i don't even know why its called an interstage! thanks for your and all others' help in helping me learn a new hobby. i have managed to amass quite a collection of philcos, 3 model 511's, 1 211 speaker,1 87lowboy,1 model 112x,1 45lowboy,1 45f,1 89lowboy,1 116x[fantastic],1 36-655,1 36-610,1 38-8,1 38-10,1 41-290,2 42-280's and many other table models.now that i typed this up i realized i'm really hooked and i'm going to need alot of advise. i glad you guys are out there and willing to help,thanks again,phil

[Ed Locker]

Since both sides of the transformer are open, none of the circuits on Ron's site will work.
That transformer has to be replaced. Try Terry's suggestion; Hammond HX124A.

Ed